Sister Mary Sulpice, who as directress of the Baltimore Academy of the Visitation stayed in her classroom until each student had mastered the day's lesson, died Sunday at age 105 of congestive heart failure at a monastery in Tyringham, Mass.

She was one of the cloistered nuns who lived and taught at the landmark walled monastery and girls academy that stood in downtown Baltimore at Park Avenue and Centre Street, later the site of the Greyhound bus station. The institution ended its days in the Poplar Hills section of Roland Park.

Until she was in her 90s, she was the first to file into the darkened pre-dawn chapel before her fellow sisters began chanting the daily office.

Born Mary Emma Offutt in on a Poolesville farm, she entered the religious life after her sister joined a convent in Chestnut Hill, a Philadelphia suburb.

"My father rode on a horse alongside the carriage to make sure I really wanted to leave," she recalled of the day she left her Montgomery County farm home.

She entered Baltimore's Visitation monastery in 1914 and took her vows two years later.

She soon began teaching at the private girls school alongside the Victorian-style convent, chapel and walled garden that faced a grouping of other academic buildings -- the old Baltimore City College and the Johns Hopkins University structures at Howard and Centre streets.

"In good conscience, I couldn't leave a classroom at the end of the day if I thought each student hadn't learned the day's lesson," she said in a 1988 interview.

Sister Sulpice was so adamant on that point that she would detain her students after regular school hours to ensure that they were properly instructed.

"I remember her as being strict, almost stern. But she was a teacher who held your interest at all times. I respected her so much I still have some of the ancient-history books we used in her year," said Mary Virginia Hall Hart, a Pikesville resident who was Sister Sulpice's student in 1926 and 1927.

"She was very slim and seemed to be held together with straight pins. She often adjusted the pins on the immaculate white garment she wore about the head and neck," Mrs. Hall said. "Her dedication to her religion was remarkable. When we were 10 years old, we thought she wore a hair shirt under her black robes because of her devotion."

"She took the religious life very seriously and lived it to the nth degree," said the Rev. Michael Roach, pastor of St. Bartholomew's Roman Catholic Church in Manchester. "Only a few years ago she told me, 'I've always tried to live what I was taught as a novice.' "

During her long career, Sister Sulpice became the directress of the school, which moved to Roland Avenue and Bellemore Road in 1927 and later admitted boys. She also held the titles of procuratrix, treasurer and counselor of the order of sisters.

She was a prolific letter writer who corresponded with her students, many of whom sought her advice. On Sunday, when they called in person, they sat separated from her by a wooden lattice screen that divided one of the cloistered monastery parlors.

In 1976, the nuns decided to sell their Roland Avenue property, and she and other sisters moved to an Order of the Visitation monastery in Wilmington, Del.

Some of her friends thought she would not make the transition, but she surprised them by continuing to be the first in the chapel each morning. "I think we've been as happy here as at any time in our lives," she said.

At that time she posed for a series of newspaper photographs that showed her clutching rosary beads near the silver Visitation cross she wore about her neck.

A Mass of Christian burial will be offered Thursday at 2 p.m. at the Monastery of the Visitation, Tyringham, Mass.